Photoengraving



Feb. 27, 1940. w. s, MARX, JR

PHOTOENGRAVING Filed May 23, 1958 INVE R.

\ Patented Feb. 27, 1940 UNITED STATES PATENT OFFICE PHOTOENGRAVING Application May 23, 1938, Serial No. 209,492

12 Claims.

This invention relates to 'photoengraving, and more particularly to a process by which a halftone (screened) negative is exposed in an ordinary engraving camera to a specially prepared drawing so as to eliminate all screening or dots in the background or highlight sections of the reproduction of such drawing. The process is particularly adaptable to the type of photoengraving and illustration commonly used for newspaper advertising.

An object of this invention is to provide a simple method of highlighting that is free from the more lengthy and inexpedient prevailing methods such as laborious hand-painting or handopaquing, special lenses and stops that are in many instances impractical and depend upon delicately balanced exposure relationships, and which are limited to certain types of drawings.

Briefly, the process consists of exposing a halftone negative element in the usual way, properly recording thereon all tones of the drawing in proper values. The negative element is then reexposed, using only ultra-violet light. A fluores cent substance, or absorbent of ultra-violet light,

having been mixed with the pigment with which the drawing was made, all tones of the drawing will now photograph as black; that is, they will have no appreciable effect on the negative element, since the ultra-violet light impinging on the ultra-violet absorbent is not reflected, while the ultra-violet light impinging upon the unpainted highlight sections of the drawing will be reflected into the lens and imaged upon the corresponding sections of the negative element. Thus, if the halftone screen has been properly moved before the ultra-violet exposure is made, the screen pattern in the highlight sections will be completely obliterated by the ultra-violet exposure. In other words, the small transparent openings between the large, overlapping highlight dots recorded on the negative element during the first exposure, will be filled up by the ultra-violet exposure, leaving, upon development of the negative, a solid, opaque tone over the highlight areas.

Throughout this application the term "highlight" is used to designate the sections of an illustration which are required to print in repro- 50 duction as pure white, or as free from screen pattern, and is usually considered as referring to background or white" sections of an illustration. Also the term "tone section refers to the shaded or dark parts of an illustration. These 55 terms are also used to indicate areas in a negative element which correspond to the designated areas or sections in the illustration.

Where possible, reference is made to the accompanying drawing.

Figure 1 may be considered as representative '5 of the type of drawing where, in printed reproduction, elimination of screen pattern is usually required in the highlight sections, examples of which are indicated by H". The tone or shaded sections are indicated by T. 10

Figure 2 represents a magnified highlight section of a halftone negative wherein no effort has been made to eliminate screen pattern in the highlights. Figure 2 clearly shows the small transparent (white) 'openings between the 16 opaque (black) dots. These openings will, of course, print as small black dots on a positive made from this section, unless they are covered up, painted over, etc.

Figure 3 represents the same highlight section as Figure 2, after the herein described ultraviolet light exposure is added to the negative element, and shows that the screen pattern is effectually removed, and a positive made from Figure 3 would yield clear whites.

Step A.An-ultra violet absorbent substance, preferably of the fluorescent type, such as quinine bisulfate is dissolved in Water, and the solution is used as a solvent for the water color or ink pigment used to make the drawing to be reproduced. Other ultra-violet absorbents, and other solvents may be used. I prefer, however, to use the colorless solution made as follows:

Distilled water cubic centimeters 1000 Quinine bisulfate grams 90 Sulfuric acid, C. P cubic centimeters 10 Egg albumen, C. P grams 15 The sulfuric acid is added to amplify fluorescent and absorbtion properties, and the albumen is m added so that the pigment with which the solution is mixed may be applied to the drawing smoothly. This solution is used in place of water as a medium and carrier for the artists pigment. If, for instance, Windsor Newtons water-color Lampblack, which is representative of the type of material used customarily in making washdrawings for newspaper advertising, is selected as a pigment, the artist would use the above solution in the same way be would ordinarily use water, to dissolve, mix, and dilute the pigment. The drawing is executed upon a surface of white paper, or an equivalent reflector of ultra-violet light.

Step B.The drawing prepared in Step A has 5 the general appearance of any ordinary wash drawing, since visible light of wave lengths greater than 400 millimicrons (l millimicron equals 0.000001 millimeter) is only negligibly aifected by reflection from quinine bisulfate. Therefore, the drawing may be photographed by the photoengraver, using visible light, in the normal way to record all tones in their proper screened values. The highlight sections or the resulting negative then appear as in Figure 2, and Step C is required to eliminate-,the screen pattern therein.

Step C.Ultra-violet light is radiated over the drawing evenly, and since ultra-violet light of wave-lengths between about 300 and 390 millimicrons is not reflected by the quinine bisulfated drawing, only the white or highlight sections not coated with quinine bisulfate reflect ultra-violet light, and become imaged upon the negative element. I prefer to advance the halftone screen before making this exposure, so that the distance between the screen and the negative element is great enough to effectually destroy projection of the screen pattern over the negative, so that the spaces between highlight dots may be filled up, or veiled over. Or, optionally, the screen may be moved in a plane parallel to the negative element to the extent of the width of one screen ruling, or the screen may be altogether removed.

The source of ultra-violet light may be any which radiates a suflicient volume of light at wave lengths longer than about 315 milirnicrons. I prefer to use ordinary "white-flame carbon arcs, which radiate amply in the ultra-violet region, or a lamp manufactured by the General Electric Company of Los Angeles, California, which consists of a high-intensity mercury-vapor argon-filled arc lamp in a double nonex or quartz nonex envelope. Light, rich in ultra-violet, is generated by electronic disturbance between two barium-oxide coated cathode elements in the inner tube.

The ordinary collodion wet-plates may be used for the halftone negative element, or Kodalith film, manufactured by the Eastman Kodak Company of Rochester, N. Y. The emulsions in these materials are sensitive in the requisite ultraviolet range, with the sensitivity peak at about 375 millirnicrons wave-length. There is no change from standard procedure in developing the negative and further processing.

Steps B and C may be optionally reversed in order.

-A proper ultra-violet transmission filter which is effectually opaque to visible light, is, of course, interposed between the light source and the negative element, in Step C.

It is understood that other substances may be used as ultra-violet absorbents, such as, for instance, anthracine, resorcin blue, eosin, etc.

I consider as within the scope of this invention modifications consisting of the use of other wave lengths of light so employed as to accomplish the same end, or for the same purpose as the preferred embodiment herein described.

I claim:

1. The method of rendering a halftone negative free from screen pattern in the highlight sections comprising, treating the remaining sections of the subject with ultra-violet light absorbent and then photographically exposing the negative to the subject so treated in the presence of ultra-violet light only.

2. The method of rendering a halftone negative free from screen pattern in the highlight sections comprising, treating the remaining sections of the subject with ultra-violet light absorbent and then photographically recording two impressions of the subject so treated upon the negative, one in the presence of visible light and the other in the presence of ultra-violet light only.

3. The method of rendering a halftone nega tive free from screen pattern in the highlight sections comprising, treating the remaining sections of the subject with ultra-violet light absorbent and then photographically recording two impressions of the subject so treated upon the negative, the first in the presence of visible light and the second in the presence of ultra-violet light only.

4. The method of rendering a halftone negative free from screen pattern in the highlight sections comprising, treating the remaining sections of the subject with ultra-violet light absorbent and then photographically recording two impressions of the subject so treated upon the negative, the first in the presence of ultra-violet light only and the second in the presence of visible light.

5. The method of making a halftone negative free from screen pattern in the highlights which comprises mixing with the pigment from which the subject to be reproduced is to be made an absorbent of ultra-violet light, photographing the subject so made on a light-sensitive element with a halftone screen in normal relation thereto, moving the screen from said normal position, and then making an auxiliary photographic exposure of the subject upon said light-sensitive element in the presence of ultra-violet light only which is reflected only from the highlight portions of the subject which are free from the ultra violet absorbent.

6. The method of making a halftone negative free from screen pattern in the highlights which comprises mixing with the pigment from which the subject to be reproduced is to be made an absorbent of ultra-violet light, photographing the subject so made on a light-sensitive element with a halftone screen in normal relation thereto, removing the screen, and then making a second photographic exposure of the subject upon said light-sensitive element with ultra-violet light only.

'7. The method of making a halftone negative free of screen pattern in the highlight sections which comprises including in the pigment from which a subject to be reproduced is to be made an absorbent of ultra-violet light, photographing the subject with a halitone screen in normal relation to a light-sensitive element, subjecting the subject to an auxiliary photographic exposure with the screen in an oil-normal position and admitting to the said light-sensitive element ultra-violet light only which is reflected from only the highlight sections of the subject which have not been coated with the ultra-violet absorbent, in suflicient quantity to veil or remove screen pattern from said sections.

8. The method of making a halftone negative free of screen pattern in the highlight sections which comprises making a drawing to be reproduced with an absorbent of ultra-violet light mixed with the pigment, photographing the drawing with a halftone screen in normal relation to a light-sensitive element and making an auxiliary photographic exposure of the drawing on the same light-sensitive element by means of ultra-violet light only for the purpose of lightstriking the highlight sections of the drawing without affecting materially the remaining portions thereof. I

9. The method of halftone photography comprising preparing the matter to be photographed with pigment containing an absorbent of ultraviolet light at all points where screen pattern is to be retained, photographing such matter so as to produce an ordinary halftone negative, and again photographing such matter on the same negative with the halftone screen position altered and with ultra-violet light only so as to produce upon said negative no appreciable efiect on the areas corresponding to those areas in the prepared matter containing the ultra-violet absorbent, and so that the remaining areas on the negative corresponding to the highlight areas of the prepared matter are additionally affected to the point of effectually efiacing the screen pattern otherwise recorded thereon.

10. The method of halftone photography which includes eliminating the screen pattern from selected sections of a halftone negative, comprising preparing the subject to be photographed with pigment containing an absorbent of ultraviolet light, photographing the subject in accordance with the usual halftone procedure, and

with pigment containing an absorbent of ultraviolet light, photographing the subject in accordance with the usual halftone procedure, and making an auxiliary photographic exposure of the subject on the same negative by means of ultra-violet light only, to record thereon an opaque deposit sufficient to efiace the screen pattern in those sections of the negative which are reproductive of the sections of the subject which contain no ultra-violet absorbent.

12. A method of making a halftone negative of 20 a subject having sections absorptive and reflective respectively of ultra-violet light comprising, imaging on the negative the usual hali'tone record of the subject and superposing on said record a second image by ultra-violet light only.

WALTER S. MARX, JR. 

